WO2014057932A1 - Process for manufacturing polishing composition, and polishing composition - Google Patents

Abstract

This process for manufacturing a polishing composition includes a step for mixing a water-soluble polymer powder with water to form a water-soluble polymer mixture, wherein the content of particles having diameters of 50μm or smaller in the water-soluble polymer powder is 40vol% or less. It is preferable that the content of particles having diameters of 10μm or smaller in the water-soluble polymer powder is less than 1vol%.

Description

Method for producing polishing composition and polishing composition

The present invention relates to a method for producing a polishing composition containing a water-soluble polymer and a polishing composition.

As types of defects observed on the polished surface after polishing with a polishing composition, LPD (Light Point Defects) and LPD-N (Light Point Defect Non-cleanable) are known. LPD means a defect generally called a particle. On the other hand, LPD-N means a defect that cannot be removed by polishing, cleaning, drying, etc., for example, a crystal defect. For example, Patent Document 1 describes that LPD is reduced by using a polishing composition having a specific ion concentration reduced.

JP 2008-053414 A

LPD-N reduction is an important issue in recent years. However, the actual situation is that there is no report yet on a method for producing a polishing composition effective for reducing LPD-N. For example, even if Patent Document 1 that discloses a polishing composition capable of reducing LPD is taken into consideration, a technical basis for predicting reduction of LPD-N cannot be found.

An object of the present invention is to provide a method for producing a polishing composition containing a water-soluble polymer and capable of easily reducing LPD-N, and a polishing composition.

In order to achieve the above object, in the first aspect of the present invention, water is mixed with a water-soluble polymer powder having a particle size of 50 μm or less and a content of particles of 40 μ% or less. And a method for producing a polishing composition comprising the step of preparing a water-soluble polymer mixture.

In the second aspect of the present invention, a water-soluble polymer mixture is prepared by mixing a water-soluble polymer powder having a particle size of 50 μm or less and a volume of 40 μ% or less with water. Polishing composition manufactured through a process is provided.

In the polishing composition production method and the polishing composition, the water-soluble polymer powder preferably has a content of particles having a particle diameter of 10 μm or less of less than 1% by volume.

In the method for producing a polishing composition and the polishing composition, the water-soluble polymer mixture is preferably basic.

The method for producing a polishing composition preferably further includes a step of mixing a silica particle mixture obtained by mixing silica particles, a basic compound, and water with the water-soluble polymer mixture. It is preferable that the said polishing composition is manufactured through this mixing process further.

The polishing composition is preferably used for polishing a silicon substrate.

The polishing is preferably final polishing of the silicon substrate.

According to the present invention, it becomes easy to reduce the LPD-N of the surface after polishing with the polishing composition.

Hereinafter, an embodiment of the present invention will be described.

The method for producing a polishing composition comprises preparing a water-soluble polymer mixture by mixing water with a water-soluble polymer powder having a particle size of 50 μm or less and a particle size of 50 μm or less. Process. The production method of the present embodiment further includes a step of mixing a silica particle mixture obtained by mixing silica particles, a basic compound, and water with a basic water-soluble polymer mixture.

The polishing composition obtained by the manufacturing method of this embodiment is a stock solution for dilution, and is suitably used for polishing a polishing object such as a silicon substrate after dilution with water. The polishing of the silicon substrate is performed, for example, by a preliminary polishing step (primary polishing and secondary polishing) for flattening the surface of a disk-shaped silicon substrate sliced from a silicon single crystal ingot, and the surface of the silicon substrate after the preliminary polishing step And a final polishing step of removing the fine irregularities present in the surface to make a mirror surface. The polishing composition of this embodiment is particularly preferably used in the step of final polishing of the silicon substrate.

In the step of preparing the water-soluble polymer mixture, the water-soluble polymer powder and water are mixed.

The water-soluble polymer has a function of improving the wettability of the polished surface after polishing with the polishing composition. The content of particles having a particle size of 50 μm or less in the water-soluble polymer powder mixed with water is 40% by volume or less, preferably 30% by volume or less, more preferably 20% by volume or less, and still more preferably. Is 10% by volume or less, most preferably 5% by volume or less. The content of particles having a particle size of 10 μm or less in the water-soluble polymer powder is preferably less than 1% by volume. By reducing the content of fine particles in the water-soluble polymer powder, LPD-N can be easily reduced.

The content of particles having a particle size of 50 μm or less and the content of particles having a particle size of 10 μm or less are based on a volume basis in which the volume of particles in the water-soluble polymer powder is accumulated in order from particles having a small particle size. In the cumulative distribution, it is measured as a cumulative rate [%] of particles having a particle size of 50 μm or less and a cumulative rate [%] of particles having a particle size of 10 μm or less.

In order to obtain a water-soluble polymer powder in which the content of fine particles is reduced as described above, for example, classification using a sieve or an air stream can be used.

The average particle size of the water-soluble polymer powder is preferably 50 μm or more, more preferably 70 μm or more, and still more preferably 100 μm or more. Generally, as the weight average molecular weight of the water-soluble polymer increases, the average particle diameter of the water-soluble polymer powder tends to increase. That is, since the weight average molecular weight increases as the average particle diameter increases, the wettability of the polished surface tends to increase.

The average particle diameter of the water-soluble polymer powder is preferably 250 μm or less, more preferably 200 μm or less, and still more preferably 150 μm or less. The smaller the average particle size, the more uniformly the water-soluble polymer is dissolved.

As the water-soluble polymer, those having at least one functional group (hydrophilic group) selected from a cationic group, an anionic group and a nonionic group in the molecule can be used. Examples of the water-soluble polymer include those containing a hydroxyl group, a carboxyl group, an acyloxy group, a sulfo group, a quaternary nitrogen structure, a heterocyclic structure, a vinyl structure, and a polyoxyalkylene structure in the molecule.

Other examples of water-soluble polymers include, for example, cellulose derivatives, imine derivatives such as poly (N-acylalkyleneimine), polyvinyl alcohol, polyvinyl pyrrolidone, copolymers containing polyvinyl pyrrolidone as part of the structure, and polyvinyl caprolactam. , Copolymers containing polyvinyl caprolactam as part of the structure, polyoxyethylene, polymers having a polyoxyalkylene structure, copolymers having a plurality of types of structures such as diblock type, triblock type, random type, and alternating type. Examples include polymers and polyether-modified silicones.

As the water-soluble polymer, one kind may be used alone, or two or more kinds may be used in combination.

Among water-soluble polymers, a cellulose derivative, polyvinyl pyrrolidone, and a polymer having a polyoxyalkylene structure are preferable because they have a good function of increasing the wettability of the polished surface. Examples of the cellulose derivative include hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and carboxymethyl cellulose. Among cellulose derivatives, hydroxyethyl cellulose is preferable because it has an excellent function of increasing the wettability of the polished surface and is easily removed in a cleaning step after polishing (that is, has good cleaning properties).

In order to suppress poor dissolution of water-soluble polymer (generation of insoluble matter), it is preferable that the hydroxyl group of the water-soluble polymer is hydrophobized with, for example, dialdehyde. Examples of the dialdehyde include oxalic acid dialdehyde (ethane dial), malonic acid dialdehyde (propane dial), and succinic acid dialdehyde (butane dial).

The weight average molecular weight of the water-soluble polymer is preferably 1000 or more in terms of polyethylene oxide, more preferably 10,000 or more, still more preferably 100,000 or more, and still more preferably 200,000 or more. As the weight average molecular weight of the water-soluble polymer increases, the wettability of the polished surface increases.

The weight average molecular weight of the water-soluble polymer is preferably 200000 or less, more preferably 1500,000 or less, still more preferably 1000000 or less, and most preferably 500000 or less. As the weight average molecular weight of the water-soluble polymer decreases, the dispersion stability of the polishing composition improves.

The weight average molecular weight of the water-soluble polymer in terms of polyethylene oxide can be measured by gel permeation chromatography (Gel Permeation Chromatography, GPC).

It is preferable that the water used in the step of preparing the water-soluble polymer mixture does not hinder the function of other components in the polishing composition. Examples of such water include water having a total content of transition metal ions of 100 ppb or less. The purity of water can be increased by operations such as removal of impurity ions using an ion exchange resin, removal of foreign matters by a filter, and distillation. Specifically, it is preferable to use, for example, ion exchange water, pure water, ultrapure water, or distilled water. In addition, in the manufacturing method of polishing composition, it is preferable that the water of the same quality is used also in processes other than the process of preparing a water-soluble polymer mixture.

In the step of preparing the water-soluble polymer mixture, water-soluble polymer powder and water are mixed in a mixing container. It is preferable that the mixing container includes a stirrer or a disperser. Examples of the stirrer or disperser include a wing stirrer, an ultrasonic disperser, and a homomixer. The capacity of the mixing container is preferably 10 to 10,000 L, for example, in consideration of production efficiency and quality stability. The mixing container is preferably made of resin. The mixing container may be made of metal, but it is preferable that at least the inner surface of the mixing container is covered with a resin layer in order to suppress the mixing of metal impurities into the polishing composition.

The content of the water-soluble polymer in the water-soluble polymer mixture is preferably 0.02% by mass or more, more preferably 0.05% by mass or more, when the total mass of the water-soluble polymer and water is 100. More preferably, it is 0.1% by mass or more. As the content of the water-soluble polymer increases, the content of the water-soluble polymer in the polishing composition can be set higher.

The content of the water-soluble polymer in the water-soluble polymer mixture is preferably 10% by mass or less, more preferably 5% by mass or less, where the total mass of the water-soluble polymer and water is 100. Yes, and more preferably 3% by mass or less. As the content of the water-soluble polymer decreases, the dispersibility of the water-soluble polymer improves.

The water-soluble polymer mixture is preferably basic. The pH of the water-soluble polymer mixture is preferably 8 or more, more preferably 9 or more, as measured at 25 ° C. As the pH of the water-soluble polymer mixture increases, the dispersibility of the silica particles is easily maintained when the water-soluble polymer mixture and the silica particle mixture are mixed.

The pH of the water-soluble polymer mixture is preferably 12 or less, more preferably 10.5 or less, as measured at 25 ° C. As the pH of the water-soluble polymer mixture decreases, dissolution of the silica particles is suppressed.

The pH of the water-soluble polymer mixture is adjusted by adding a basic compound to the water-soluble polymer mixture. The basic compound is preferably the same as the basic compound used as a raw material for the silica particle mixture.

The water-soluble polymer mixture is preferably filtered in order to reduce foreign matters or aggregates contained in the mixture. Filtration can be performed by a conventional method using a filter. The material and structure of the filter used for filtration are not particularly limited. Examples of the filter material include cellulose, polyamide, polysulfone, polyethersulfone, polypropylene, polytetrafluoroethylene (PTFE), polycarbonate, and glass. Examples of the filter structure include a depth filter, a pleated filter, and a membrane filter.

The filter used for filtration can be selected based on the opening. The aperture of the filter is preferably 0.05 μm or more, more preferably 0.1 μm or more, and further preferably 0.2 μm or more. The greater the filter opening, the better the filtration efficiency.

The opening of the filter is preferably 100 μm or less, more preferably 20 μm or less, further preferably 10 μm or less, more preferably 5 μm or less, still more preferably 2 μm or less, and most preferably 1 μm or less. As the opening of the filter becomes smaller, a polishing composition with higher quality can be obtained.

In addition, the nominal value of the opening of the filter is provided by the filter manufacturer.

The filtration of the water-soluble polymer mixture may be natural filtration performed at normal pressure, suction filtration, pressure filtration, or centrifugal filtration.

The water-soluble polymer mixture obtained in the step of preparing the water-soluble polymer mixture is mixed with the silica particle mixture.

The silica particle mixture is prepared by mixing silica particles, a basic compound, and water. The silica particle mixture is prepared in a step different from the step of preparing the water-soluble polymer mixture. In the step of preparing the silica particle mixture, silica particles, a basic compound, and water are mixed in a mixing container. In the step of preparing the silica particle mixture, the order of mixing the raw materials is not particularly limited. In the step of preparing the silica particle mixture, an aqueous dispersion of silica particles may be used as a raw material, or an aqueous solution of a basic compound may be used. That is, in the step of preparing the silica particle mixture, other raw materials may be mixed with the water first supplied alone in the mixing container, or an aqueous dispersion of silica particles or an aqueous solution of a basic compound is first added to the mixing container. The other raw materials may be mixed thereafter.

Since the mixing container used in the step of preparing the silica particle mixture can be the same as the mixing container used in the step of preparing the water-soluble polymer mixture, detailed description thereof is omitted.

Silica particles have a function of mechanically polishing the surface to be polished. Examples of the silica particles include colloidal silica, fumed silica, and sol-gel silica. One kind of silica particles may be used alone, or two or more kinds may be used in combination.

Among the silica particles, when colloidal silica or fumed silica is used, particularly when colloidal silica is used, scratches generated on the polished surface of the silicon substrate are reduced.

The average primary particle diameter of the silica particles is preferably 5 nm or more, more preferably 10 nm or more, and further preferably 20 nm or more. As the average primary particle diameter of the silica particles increases, the polishing rate improves.

The average primary particle diameter of the silica particles is preferably 100 nm or less, more preferably 70 nm or less, and even more preferably 50 nm or less. As the average primary particle diameter of the silica particles decreases, the dispersion stability of the polishing composition improves.

The primary particle diameter of the silica particles can be calculated based on a photograph taken with a scanning electron microscope such as S-4700 manufactured by Hitachi High-Technologies Corporation. For example, a predetermined number (eg, 100 or more) of silica particle images are randomly selected from an electron micrograph of silica particles taken at a magnification of 10,000 to 50,000 times. The area of the image of the selected silica particle is measured, and the diameter of a circle having the same area as that area is obtained as the primary particle diameter of the silica particle. The average primary particle diameter of the silica particles is calculated as an average value of primary particle diameters thus obtained (50% particle diameter in a volume-based integrated fraction). In addition, calculation of a primary particle diameter and an average primary particle diameter can be performed using a commercially available image analyzer.

The average secondary particle diameter of the silica particles is preferably 10 nm or more, more preferably 20 nm or more, and further preferably 30 nm or more. As the average secondary particle diameter of the silica particles increases, the polishing rate improves. The average secondary particle diameter of the silica particles is preferably 200 nm or less, more preferably 150 nm or less, and still more preferably 100 nm or less. As the average secondary particle diameter of the silica particles decreases, the dispersion stability of the polishing composition improves. The average secondary particle diameter of the silica particles can be measured, for example, by a dynamic light scattering method using FPAR-1000 manufactured by Otsuka Electronics Co., Ltd.

The content of silica particles in the silica particle mixture is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 5% by mass when the total amount of silica particles, basic compound, and water is 100. % Or more. As the content of the silica particles increases, the content of the silica particles in the polishing composition can be set higher.

The content of silica particles in the silica particle mixture is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass when the total amount of silica particles, basic compound, and water is 100. % Or less. As the content of the silica particles decreases, the dispersibility of the silica particles tends to be maintained during mixing with the water-soluble polymer mixture.

The basic compound has a function of chemically polishing the surface to be polished. Further, the basic compound has a function of improving the dispersion stability of the polishing composition.

Examples of basic compounds include alkali metal hydroxides, quaternary ammonium hydroxides or salts thereof, ammonia, and amines. Examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide. Examples of the quaternary ammonium hydroxide or a salt thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. Examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, Examples include piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, and guanidine.

A basic compound may be used individually by 1 type, and may be used in combination of 2 or more type.

The basic compound is preferably at least one selected from ammonia, an alkali metal hydroxide, and a quaternary ammonium hydroxide.

The basic compound is more preferably at least one selected from ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide, and more preferably at least one of ammonia and tetramethylammonium hydroxide. And most preferably ammonia.

The content of the basic compound in the silica particle mixture is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, when the total amount of silica particles, basic compound, and water is 100. More preferably, it is 0.1 mass% or more. As the content of the basic compound increases, the dispersibility of the silica particles is easily maintained during mixing with the water-soluble polymer mixture.

The content of the basic compound in the silica particle mixture is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3 when the total amount of silica particles, basic compound, and water is 100. It is below mass%. As the content of the basic compound decreases, the content of the basic compound in the polishing composition can be set lower.

The water in the silica particle mixture acts as a dispersion medium for silica particles and a solvent for basic compounds. Since the water used in the step of preparing the silica particle mixture can be the same as the water used in the step of preparing the water-soluble polymer mixture, detailed description thereof is omitted.

The silica particle mixture obtained in the step of preparing the silica particle mixture is mixed with the water-soluble polymer mixture. The mixing of the silica particle mixture and the water-soluble polymer mixture in the present embodiment includes a step of supplying the silica particle mixture into the mixing vessel and a step of supplying the water-soluble polymer mixture into the same mixing vessel. Since the mixing container used here can be the same as the mixing container used in the step of preparing the water-soluble polymer mixture, detailed description thereof is omitted.

In the present embodiment, the process of supplying the water-soluble polymer mixture is started after the process of supplying the silica particle mixture to the mixing container is completed. The completion of the step of supplying the silica particle mixture means that the supply pump provided in the pipe for supplying the silica particle mixture to the mixing container is stopped, the valve provided in the pipe is closed, or supplied. The point when the silica particle mixture is exhausted.

The stirring operation or dispersing operation in the mixing container by the stirrer or the dispersing machine may be continuously performed in the step of supplying the silica particle mixture to the mixing container and the step of supplying the water-soluble polymer mixture to the mixing container. It may be done intermittently. The stirring operation or dispersing operation in the mixing vessel is preferably continued after the step of supplying the silica particle mixture is completed until the step of supplying the water-soluble polymer mixture is completed. Furthermore, the stirring operation or the dispersing operation in the mixing container is preferably continued even after the step of supplying the water-soluble polymer mixture is completed in order to obtain a polishing composition with higher dispersibility.

The supply speed of the step of supplying the silica particle mixture and the step of supplying the water-soluble polymer mixture is set in accordance with, for example, supply efficiency and supply equipment such as a pump.

The supply rate of the water-soluble polymer in the step of supplying the water-soluble polymer mixture is preferably 1 part by mass / min or more, more preferably 3 parts by mass / min or more with respect to 100 parts by mass of the silica particles. More preferably, it is 5 parts by mass / min or more. As the supply rate of the water-soluble polymer increases, the time required for the step of supplying the water-soluble polymer mixture can be shortened.

The supply rate of the water-soluble polymer in the step of supplying the water-soluble polymer mixture is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, with respect to 100 parts by mass of the silica particles. More preferably, it is 10 parts by mass / min or less. As the supply rate of the water-soluble polymer decreases, it becomes easier to disperse the water-soluble polymer.

At least one of the silica particle mixture and the water-soluble polymer mixture may contain components other than those described above. In addition, the method for producing the polishing composition is a container containing a mixture of a surfactant, an organic acid, an organic acid salt, an inorganic acid, an inorganic acid salt, and a chelating agent other than the silica particle mixture and the water-soluble polymer mixture. You may have the supply process supplied to.

Surfactant has a function of improving the dispersibility and polishing performance of the polishing composition.

Examples of the surfactant include ionic or nonionic surfactants having a weight average molecular weight of less than 1000. Among the surfactants, nonionic surfactants are preferably used.

Examples of nonionic surfactants include oxyalkylene polymers such as polyethylene glycol and polypropylene glycol, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl amine, polyoxyethylene fatty acid ester, polyoxyethylene. Examples include polyoxyalkylene adducts such as glycerether fatty acid esters and polyoxyethylene sorbitan fatty acid esters. More specifically, polyoxyethylene polyoxypropylene copolymer, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, Polyoxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene Stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene Phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, poly Oxyethylene stearylamide, polyoxyethylene oleylamide, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, monolaurin Acid polyoxyethylene sorbitan, monopalmitic acid polyoxyethylene sorbita Polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitol tetraoleate, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, and acetylene glycol Can be mentioned.

Surfactant may be used alone or in combination of two or more.

Examples of the organic acid include fatty acids such as formic acid, acetic acid and propionic acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, organic Examples include sulfonic acid and organic phosphonic acid. Examples of organic acid salts include alkali metal salts such as sodium salts and potassium salts of organic acids, and ammonium salts.

Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of the inorganic acid salt include alkali metal salts such as sodium salt and potassium salt of inorganic acid, and ammonium salt.

Organic acids and salts thereof and inorganic acids and salts thereof may be used alone or in combination of two or more.

The mixture obtained by mixing the silica particle mixture and the water-soluble polymer mixture is preferably filtered in a filtration step after being discharged from the mixing container. The filtration step can be performed by a conventional method using a filter. The filtration step can be performed in the same manner as the filtration of the water-soluble polymer mixture. The opening of the filter used in the filtration step is preferably 0.05 μm or more, more preferably 0.1 μm or more. The greater the filter opening, the better the filtration efficiency. The aperture of the filter used in the filtration step is preferably 1 μm or less, more preferably 0.45 μm or less, and still more preferably 0.2 μm or less. As the aperture of the filter becomes smaller, it becomes easier to obtain a polishing composition with higher quality.

The polishing composition of the present embodiment is accommodated in a container for transportation or storage. When the polishing composition is used, it is diluted with water or a basic aqueous solution. As the basic aqueous solution, a solution obtained by dissolving the above basic compound in water can be used. The dilution factor is preferably 2 times or more, more preferably 5 times or more, and further preferably 10 times or more. As the dilution ratio increases, the transportation cost of the polishing composition before dilution is reduced, and the storage space can be saved. The dilution factor is preferably 100 times or less, more preferably 50 times or less, and still more preferably 40 times or less. As the dilution factor decreases, the stability of the polishing composition before dilution is easily maintained.

The pH of the polishing composition before dilution is preferably in the range of 10 to 12, and the pH of the polishing composition at the time of use after dilution is preferably in the range of 10 to 11.

The content of the water-soluble polymer in the polishing composition at the time of use (after dilution) is preferably 0.002% by mass or more, more preferably 0.004% by mass or more, and still more preferably 0.8. It is 006 mass% or more. As the content of the water-soluble polymer increases, the wettability of the polished surface increases.

The content of the water-soluble polymer in the polishing composition at the time of use is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and further preferably 0.1% by mass or less. is there. As the content of the water-soluble polymer decreases, the dispersion stability of the polishing composition is easily ensured.

The content of silica particles in the polishing composition at the time of use is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and further preferably 0.3% by mass or more. As the content of silica particles increases, the polishing rate improves.

The content of silica particles in the polishing composition at the time of use is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less. As the silica particle content decreases, the dispersion stability of the polishing composition improves.

The content of the basic compound in the polishing composition at the time of use is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, and further preferably 0.003% by mass or more. . As the content of the basic compound increases, the function of chemically polishing the surface to be polished increases, and the dispersion stability of the polishing composition is easily secured.

The content of the basic compound in the polishing composition at the time of use is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.2% by mass or less. . As the content of the basic compound decreases, the smoothness of the polished surface improves.

For polishing using the polishing composition, for example, a single-side polishing apparatus or a double-side polishing apparatus can be used. The polishing pad used for polishing is not particularly limited in terms of its material, physical properties such as hardness and thickness. The polishing pad may be, for example, any type of polyurethane type, non-woven fabric type, and suede type. Further, the polishing pad may include abrasive grains or may not include abrasive grains.

The silicon substrate after the final polishing step is subjected to, for example, a rinsing step and then washed with a chemical solution and dried, whereby a silicon substrate that is a semiconductor substrate as a polishing product is obtained. In the rinsing step, for example, a rinsing composition containing the above-described water-soluble polymer, surfactant, or the like, or water is used.

Next, the operation of the method for producing a polishing composition will be described.

In the polished surface of a silicon substrate, the increase in the number of defects called LPD-N may be caused by water-soluble polymer powder used as a raw material for the polishing composition. In this regard, the present inventors have found that particles having a small particle size contained in a water-soluble polymer powder are related to LPD-N. And the manufacturing method of the polishing composition of this embodiment mixes the powder of water-soluble polymer whose content of the particle | grains which have a particle diameter of 50 micrometers or less is 40 volume% or less, and water, and is water-soluble. A step of preparing a polymer mixture. That is, by using a water-soluble polymer powder with a small content of particles having a small particle size, the generation of substances causing LPD-N and the substance causing LPD-N remain on the polished surface. It is speculated that this will be suppressed.

According to this embodiment described in detail above, the following effects are exhibited.

(1) A method for producing a polishing composition comprises mixing a water-soluble polymer powder having a particle size of 50 μm or less and a water-soluble polymer powder having a particle size of 40% by volume or less with water and mixing the mixture with water. The process of preparing. According to the polishing composition obtained by this production method, LPD-N can be easily reduced.

(2) When the content of particles having a particle diameter of 10 μm or less in the water-soluble polymer powder is less than 1% by volume, LPD-N can be further reduced easily.

(3) Since the water-soluble polymer mixture is basic, it becomes easy to reduce LPD-N by a polishing composition obtained by mixing a water-soluble polymer mixture and, for example, a silica particle mixture.

(4) The method for producing a polishing composition includes a step of mixing a water-soluble polymer mixture and a silica particle mixture. According to the polishing composition obtained by this production method, LPD-N can be easily reduced while performing chemical polishing with a basic compound and mechanical polishing with silica particles.

(5) By using the polishing composition for the purpose of polishing a silicon substrate, particularly for the purpose of final polishing of the silicon substrate, it becomes easy to obtain a silicon substrate with reduced LPD-N.

(Example of change)
The embodiment may be modified as follows.

The step of supplying the water-soluble polymer mixture is started after the step of supplying the silica particle mixture is started until it is completed instead of starting after the step of supplying the silica particle mixture is completed. Also good.

The step of supplying the water-soluble polymer mixture may be started simultaneously with the step of supplying the silica particle mixture. Alternatively, the step of supplying the silica particle mixture may be started after the step of supplying the water-soluble polymer mixture is started.

The water-soluble polymer mixture may be neutral instead of basic.

The method for producing the polishing composition is not the production of a polishing composition that is used after being diluted, but a polishing composition that contains each component in a preferred amount at the time of use and can be used without dilution. It may be applied to the manufacture of goods.

-The polishing composition obtained by the manufacturing method of the said polishing composition can also be used for the use added to the used polishing composition after using for grinding | polishing.

· The polishing composition may be used for polishing an object to be polished other than a silicon substrate. Examples of the polishing object other than the silicon substrate include metals such as stainless steel, silicon oxide substrates, plastic substrates, glass substrates, and quartz substrates.

The polishing composition can also contain abrasive grains other than silica particles. Examples of the abrasive grains other than the silica particles include alumina particles, zirconia particles, ceria particles, and titania particles. Silica particles and other particles may be used in combination. The surface of the abrasive grains may be chemically modified. When the abrasive composition contains abrasive grains other than silica particles, the step of supplying abrasive grains to the mixing container may be performed before or after the step of supplying the water-soluble polymer mixture to the mixing container, It may be performed simultaneously with the step of supplying the water-soluble polymer mixture.

The technical idea that can be grasped from the above embodiment is described below.

(I) A method for producing a polishing composition further comprising a step of supplying the silica particle mixture into a mixing vessel and a step of supplying the water-soluble polymer mixture into the same mixing vessel.

(II) The process for supplying the water-soluble polymer mixture into the mixing container is a method for producing a polishing composition that is started after the process of supplying the silica particle mixture into the mixing container.

Next, the embodiment will be specifically described with reference to examples and comparative examples.

(Examples 1 to 4 and Comparative Example 1)
In Examples 1 to 4 and Comparative Example 1, as a first step, a silica particle mixture is supplied into a mixing vessel equipped with a stirrer, and after the completion, as a second step, a water-soluble polymer mixture is put into the same mixing vessel. Was further supplied. The polishing composition as a mixture thus obtained was continuously stirred until it became uniform.

The silica particle mixture was produced by mixing colloidal silica dispersion (concentration 20% by mass) with pH 7.0 and 29% ammonia water. The pH of the silica particle mixture was 10.3. The average primary particle diameter of the silica particles was 35 μm as a result of determination using a scanning electron microscope “S-4700” manufactured by Hitachi, Ltd.

The water-soluble polymer mixture was produced by mixing dialdehyde-treated hydroxyethyl cellulose powder, water, and 29% ammonia water. The pH of the water-soluble polymer mixture was 10.0.

　表１の“工程の種類”欄に記載する“Ａ”は、シリカ粒子混合物を混合容器に供給する工程を示し、“Ｂ”は、水溶性高分子混合物を混合容器に供給する工程を示す。

“A” described in the “type of process” column of Table 1 indicates a process of supplying the silica particle mixture to the mixing container, and “B” indicates a process of supplying the water-soluble polymer mixture to the mixing container.

“Content of particles of 50 μm or less” and “Content of particles of 10 μm or less” in Table 1 respectively indicate the content of particles having a particle diameter of 50 μm or less and the particle diameter of 10 μm or less in the hydroxyethyl cellulose powder. The result of having measured content of the particle | grains to have by Microtrac MT3000 (brand name) by Nikkiso Co., Ltd. is shown.

The compositions obtained in Examples 1 to 4 and Comparative Example 1 were filtered under the conditions shown in Table 2.

　実施例１～４及び比較例１の各研磨用組成物を水で２０倍に希釈した。希釈後の研磨用組成物は、シリカ粒子の含有量が０．５質量％であり、アンモニアの含有量が０．０１質量％であり、ヒドロキシエチルセルロースの含有量が０．０１質量％であった。

The polishing compositions of Examples 1 to 4 and Comparative Example 1 were diluted 20 times with water. The diluted polishing composition had a silica particle content of 0.5 mass%, an ammonia content of 0.01 mass%, and a hydroxyethylcellulose content of 0.01 mass%. .

Next, the surface of the silicon substrate was polished under the conditions shown in Table 3 using the diluted polishing composition. The silicon substrate has a diameter of 300 mm, a conductivity type of P-type, a crystal orientation of <100>, a resistivity of 0.1 Ω · cm or more and less than 100 Ω · cm, and a polishing slurry manufactured by Fujimi Incorporated (trade name: It was pre-polished using GLANZOX 1103).

　シリコン基板の研磨面におけるＬＰＤ－Ｎをケーエルエー・テンコール社製のウェーハ検査装置“Surfscan SP2”を用いて、同装置のＤＣＯモードで計測した。その結果を表１の“欠陥（ＬＰＤ－Ｎ）の個数”欄に示す。

The LPD-N on the polished surface of the silicon substrate was measured in the DCO mode of the same apparatus using a wafer inspection apparatus “Surfscan SP2” manufactured by KLA-Tencor. The results are shown in the column “Number of defects (LPD-N)” in Table 1.

As shown in Table 1, the number of LPD-N in Examples 1 to 4 was smaller than that in Comparative Example 1.

Claims (12)

Polishing characterized by comprising a step of preparing a water-soluble polymer mixture by mixing water with a water-soluble polymer powder having a particle size of 50 μm or less and a particle size of 50 μm or less. A method for producing a composition. The method for producing a polishing composition according to claim 1, wherein the water-soluble polymer powder contains less than 1% by volume of particles having a particle diameter of 10 µm or less. The method for producing a polishing composition according to claim 1 or 2, wherein the water-soluble polymer mixture is basic. The method for producing a polishing composition according to claim 3, further comprising a step of mixing a silica particle mixture obtained by mixing silica particles, a basic compound, and water with the water-soluble polymer mixture. The said polishing composition is a manufacturing method of the polishing composition as described in any one of Claims 1-4 used for the use which grind | polishes a silicon substrate. The method for producing a polishing composition according to claim 5, wherein the polishing is final polishing of a silicon substrate. It is manufactured through a step of mixing a water-soluble polymer powder having a particle diameter of 50 μm or less with a water content of 40% by volume or less and water to obtain a water-soluble polymer mixture. Polishing composition. The polishing composition according to claim 7, wherein the water-soluble polymer powder contains less than 1% by volume of particles having a particle diameter of 10 µm or less. The polishing composition according to claim 7 or 8, wherein the water-soluble polymer mixture is basic. The polishing composition according to claim 9, wherein the polishing composition is further produced by mixing a silica particle mixture obtained by mixing silica particles, a basic compound, and water with the water-soluble polymer mixture. The said polishing composition is a polishing composition as described in any one of Claims 7-10 used for the use which grind | polishes a silicon substrate. The polishing composition according to claim 11, wherein the polishing is a final polishing of a silicon substrate.